Cook pasta in a large pot of boiling water, according to package instructions, until tender.
Meanwhile, heat olive oil in a large skillet over medium heat. Add onion, garlic and red pepper flakes. Cook, stirring occasionally, until onion gets trasnlucent, about 2 minutes.
Add tomatoes, chopped kale, parsley, sugar, salt and ¼ cup water. Stir and bring to a simmer. Cover and let cook for about 12 minutes or slightly thickened.To chop kale, start with one leaf at a time. First, remove the central rib, then slice the tender leaf into small, bite-sized pieces.
Toss in the cooked pasta and butter. Season to taste with salt, sugar and red pepper flakes.
Serve immediately topped with a generous portion of grated parmesan cheese.
Video
Notes
Use good quality tomatoes. For a richer taste and lower acidity, use the highest-quality canned tomatoes you can find. San Marzano or Bianco Di Napoli are top choices that will elevate the flavor of your dish significantly.Adjust the level of spice: I use around a teaspoon of red pepper flakes in this recipe